Thermovoltaic Cells Harvest Heat in the Dark and Turn it into Electricity

PV can only convert a small portion of the energy spectrum of sunlight to electricity. But physicists have discovered radical new properties in a nanomaterial, opening new possibilities for highly efficient thermophotovoltaic cells that could harvest heat in the dark and turn it into electricity.

The research team from Australia National University CUDOS and the University of California Berkeley demonstrated a new artificial material, or metamaterial, that glows in an unusual way when heated.

The findings could drive a revolution in the development of cells which convert radiated heat into electricity, known as thermophotovoltaic cells.

“Thermophotovoltaic cells have the potential to be much more efficient than solar cells,” said Dr Sergey Kruk from the ANU Research School of Physics and Engineering.

“Our metamaterial overcomes several obstacles and could help to unlock the potential of thermophotovoltaic cells.”

Thermophotovoltaic cells have been predicted to be more than twice as efficient as conventional solar cells. They do not need direct sunlight to generate electricity, and instead can harvest heat from their surroundings in the form of infrared radiation.

They can also be combined with a burner to produce on-demand power or can recycle heat radiated by hot engines.

The team’s metamaterial, made of tiny nanoscopic structures of gold and magnesium fluoride, radiates heat in specific directions.

The geometry of the metamaterial can also be tweaked to give off radiation in specific spectral range, in contrast to standard materials that emit their heat in all directions as a broad range of infrared wavelengths. This makes the new material ideal for use as an emitter paired with a thermophotovoltaic cell.

The project started when Dr Kruk predicted the new metamaterial would have these surprising properties. The ANU team then worked with scientists at the University of California Berkeley, who have unique expertise in manufacturing such materials.

“To fabricate this material the Berkeley team were operating at the cutting edge of technological possibilities,” Dr Kruk said.

“The size of an individual building block of the metamaterial is so small that we could fit more than 12,000 of them on the cross-section of a human hair.”